1. Field of the Invention
The present invention is directed to copper-nickel-tin alloy compositions containing rhenium as an additive and to the method of producing the alloy.
2. Description of the Prior Art
In 1933, J. T. Eash and C. Upthegrove presented a paper titled "The Copper-rich Alloys of the Copper-nickel-tin System", Transactions of the Institute of Metals Division, American Institute of Mining and Metallurgical Engineers, Volume 104, 1933, pp. 221-252. In that paper they stated that nickel additions to copper-tin bronzes produced better castings and also yielded alloys whose properties could be varied by precipitation hardening; and they also presented a series of quasibinary Cu-Ni-Sn phase diagrams to establish the alpha-phase boundaries in alloys containing from 0 to 20 percent nickel; they also stated equilibrium conditions which would exist in alloys containing up to 31 percent tin. In 1934, E. M. Wise and J. T. Eash, in a paper titled "Strength and Aging Characteristics of the Nickel Bronzes", Transactions of the Institute of Metals Division, American Institute of Mining and Metallurgical Engineers, Volume III, 1934, pp. 218-244, disclosed the age-hardening characteristics of the Cu-Ni-Sn alloys in wrought forms and further outlined solution heat treatments, effects of quenching, cold working and aging cycles which are required to achieve ultimate properties.
In the written discussions which are recorded at page 249 of the presentation of the work by Eash and Upthegrove in 1933, W. B. Price discussed the prior disclosure of the age-hardening capabilities for the Cu-Ni-Sn system, and also stated that the addition of other elements, such as Cr, Si, Mn, and Zn, in varying amounts from 0.2% to 2%, would improve strength or increase age-hardening.
Copper base alloys with nickel and tin are today generally known in the art to exhibit good combinations of strength and resistance to stress relaxation, particularly when the alloys are carefully processed under controlled conditions which serve to combine the effects of solution heat treatment, controlled quenching, cold reduction and aging so as to bring about a spinodal structure in the alloy.
It has heretofore been suggested that the best combination of properties could only be obtained when the recrystallized structure was controlled in such a manner so as to avoid large grain structure prior to cold rolling. Accordingly, several recent patents have issued which disclose not only various processing techniques but also the additions of Fe, Co, Zn, V, Cr, Si and other specific additives to the Cu-Ni-Sn alloys for the purpose of refining and controlling the grain size of these alloys both in the cast state as well as during subsequent recrystallization processing.
For instance, U.S. Pat. No. 3,941,620 to Pryor et al. discloses the additions of 0.1% to 3% Fe or Co to aid in grain refinement, while U.S. Pat. Nos. 4,052,204, 4,090,890, 4,130,421, 4,142,918 and 4,260,432 to J. T. Plewes state that Fe, Zr, Mn, Zn, Nb, Cr, Al, Mg, Mo, Ta and V, in the ranges of 0.02 to 10%, may be added to the Cu-Ni-Sn alloys as effective for producing a finer grain structure when incorporated with special heat treating cycles. U.S. Pat. No. 4,073,667 to Caron et al. also teaches that Zr, Hf, Be, Va, Nb, Ta, Cr, Mo, W, Zn and Fe may be added as element additions, in amounts of from 0.01% to 10%, to Cu-Ni-Sn alloys so as to obtain additional solution strengthening as well as work and precipitation hardening. It is also suggested that these additive elements may improve cold forming and wrought properties.
U.S. Pat. Nos. 3,937,638 and 4,012,240 also disclose a particular treatment process of Cu-Ni-Sn alloys which essentially involves homogenizing and cold working to obtain a predominantly spinodal structure in the treated alloy.
As noted, in these recent disclosures it has been proposed that a uniformly fine grain structure, whether induced by special heat treatment cycles or by alloy control, is desirable to enhance working of the cast metal. Also, where the finer grain is retained through processing and carried through to the finished product, it may impart improved properties and service life.
It has been observed, however, that the use of the specific additions to Cu-Ni-Sn alloys which are taught in the above disclosures nevertheless results in grain structure of the cast and worked alloys which is still relatively coarse, especially when the casting or pouring temperature is conducted in excess of 2350.degree. F. This coarse grain is produced even in the presence of trace elements, such as Mg and Mn in quantities of 0.01%-0.15%, which have been mentioned in, for instance, U.S. Pat. Nos. 4,052,204 and 4,142,918 as effective in producing fine grain structure. Even finer grain structure in the as cast metal is desirable. It has also been found that additional improvements in the cold working characteristics of the resulting alloys made in accord with the discussed disclosures are desireable. Similarly, improvements in ultimate tensile and yield strength are also desired, particularly for strip material which is made by standard processing procedures. More particularly, improvements are desired for such alloys in the ability to obtain finer grain structure in the cast material, in the ability to retain the as-cast fine grain structure through the full solution heat treatment cycle, and also in the ability to obtain a fine recrystallized grain structure after a cold working operation, as well as the degree to which an annealed casting may be cold rolled without causing severe cracking, especially edge cracking.